Short communication — Kort berig

The resurgence of trypanosomosis in

S P Sharmaa, T C Loshoa, M Malaub, K G Mangatea, K B Linchwea, W Amanfua and T K Motsub

0.76 (SE) and 27.29 ± 1.52 (SE) per cent in ABSTRACT Maun and respectively. The No sleeping sickness or nagana cases have been reported in Botswana since 1985. In view of infection rate was significantly higher in several confirmed clinical cases of nagana and reports of heavy bovine mortality, a Shakawe than Maun (P2 151.4, P < 0.01). parasitological survey was conducted to determine the prevalence of trypanosome The greatest numbers of infected animals infection in cattle in Maun and Shakawe areas of Ngamiland district. Wet blood films, buffy were detected in the and Seronga coat and Giemsa-stained thick and thin blood smears were used to detect trypanosomes in extension areas of Maun and Shakawe animals. Overall,trypanosome infection rate was 15.98%, with 5.94% and 27.29% in Maun respectively. None of the goats and don- and Shakawe respectively. The urgent need to combat trypanosomosis in Ngamiland, keys tested positive for trypanosomes. particularly in the Shakawe area, is highlighted, and a 3-phase integrated tsetse control The overall infection rates between strategy for this disease problem is discussed. males and females among bovines were Key words: anaemia, Botswana, cattle, haematocrit, nagana, Ngamiland, tsetse fly almost identical. Of 507 young (<18 resurgence, trypanosomosis. months) and 1302 adult cattle sampled, 53 Sharma S P,Losho T C, Malau M, Mangate K G, Linchwe K B, Amanfu W, Motsu T K The and 236 were positive, demonstrating re- resurgence of trypanosomosis in Botswana. Journal of the South African Veterinary spective infection rates of 10.45 ±1.36 (SE) Association (2001) 72(4): 232–234 (En.). National Veterinary Laboratory, Private Bag 0035, and 18.13 ±1.07 (SE) percent. Our obser- , Botswana. vations are in agreement with several previous studies7,8,19. Comparing the different parasitological African trypanosomosis, commonly particularly cattle, in the Maun and techniques used in the survey, the exami- known as nagana in animals and sleeping Shakawe areas of the Ngamiland district. nation of buffy coat proved to be the most sickness in humans, continues to be a A parasitological survey was conducted sensitive, detecting 82.5% of the positive serious threat in over 10 million km2 of from April to June 2000 in the Ngamiland animals followed by wet blood film sub-Saharan Africa. In southern Africa, district as a result of farmers’ complaints (60.5%), thick smears (49.1%) and thin trypanosomosis is also a significant ani- of cattle deaths and the diagnosis of smears (43.6%), an observation that is in mal health problem that has a profound trypanosomosis in parts of the district. agreement with other reports3,6,16.Inour impact on sustainable rural development During this survey, 1824 animals, com- opinion, the buffy coat technique is more and economic growth. The disease is prising 1809 cattle, 10 goats and 5 donkeys useful because haematocrit values could transmitted between animals mainly of various ages and both sexes from 49 also be recorded for individual animals by blood-sucking tsetse flies (Glossina crush-pens, were screened for the pres- and herd after centrifugation. At the herd morsitans centralis), which are confined to ence of trypanosome parasites in the level, the haematocrit profile or the herd the and the associated blood. Details of veterinary districts, average packed cell volume is considered Kwando/Linyati River system in the extension areas and cattle crush-pens a useful indicator of trypanosome infec- Ngamiland and Chobe districts of sampled are presented in Fig. 1. Animals tion and herd health. Owing to clotting Botswana. were selected randomly from different and/or haemolysis of 11 blood samples, Neither sleeping sickness nor nagana crush-pens. Blood samples were collected wet blood films and buffy coats could not has been reported in Botswana since 1985. in vacutainers, with and without antico- be examined. However, thick and thin This is largely due to concerted efforts agulant, from the ear and jugular veins of blood smears of 7 such animals were to eradicate tsetse flies by the Tsetse animals for parasitological and sero- examined microscopically. Trypano- Control Division (TCD) of the Depart- logical examination. Parasitological stud- somes were detected in 74 animals by ment of Animal Health and Production. ies included examination of wet blood using all 4 techniques, whereas 50, 70 and In November 1999 and the first quarter of films, determination of microhaematocrit 95 animals were diagnosed positive by 3, the year 2000, several clinical cases of (HCT) values, and examination of buffy 2, and 1 of the laboratory techniques re- nagana among cattle from Ngamiland coat, thick, and thin blood smears after spectively. Although direct demonstra- were confirmed at the National Veterinary staining with Giemsa, following standard tion of trypanosomes in the infected Laboratory in Gaborone. Recent reports laboratory techniques. The data were animals by the techniques used in this from TCD have also indicated the exten- analysed statistically using standard investigation provided conclusive proof sion of the tsetse fly range beyond origi- statistics, namely mean, proportions, and of infection, these techniques have been nally known areas. In view of this, a standard error (SE), and Chi-square tests reported not to be as sensitive as some of survey was conducted to determine the for comparison of proportions17. the recently-introduced techniques such prevalence of trypanosomosis in animals, Trypanosomes were observed in blood as AG-ELISA and polymerase chain reac- samples of 289 of 1809 cattle representing tion (PCR)18. Parasitological techniques aNational Veterinary Laboratory, Private Bag 0035, an infection rate of 15.98 ± 0.86 (SE) per cannot be used to detect latent trypa- Gaborone, Botswana. cent in Ngamiland. In total, 57 of 959 and nosome infection as most of the field in- bTsetse Control Division, Department of Animal Health and Production, Private Bag 0014, Maun, Botswana. 232 of 850 cattle were positive for trypano- fections are not associated with patent 14 Received: January 2001. Accepted: September 2001. somes, indicating infection rates of 5.94 ± parasitaemia . New technologies such as

232 0038-2809 Tydskr.S.Afr.vet.Ver. (2001) 72(4): 232–234 Fig.1: Veterinary districts, extension areas and crushpens in Ngamiland covered during trypanosomosis survey.

AG-ELISA and PCR, with some improve- enzymes, fever, complement and the administration of diminazine acetu- ment, are likely to revolutionise the diag- trypanosomal antigen produced by rate to cattle might have influenced the nosis of trypanosomosis in animals, trypanosomes 12,13. prevalence rate of trypanosome infection 10 humans and tsetse flies . However, .Morphologically, trypanosome para- recorded during this survey. according to a report, the sensitivity of sites identified during this survey were Based on the results of the present parasitological and PCR techniques was predominantly Trypanosoma brucei survey, an overall prevalence rate of approximately the same in detecting (52.5%), followed by Trypanosoma congo- 15.98% in Ngamiland and a significantly Trypanosoma vivax infection in cattle5. lense (36.2%) and Trypanosoma vivax higher trypanosome infection rate of Mean per cent haematocrit values of (11.3%). We did not attempt to differenti- 27.29% in Shakawe in particular is a cause trypanosomosis-positive and negative ate between human and animal sub- for concern. The Department of Animal cases in Maun were 20.87 ± 0.16 (SE) species of T. brucei. More research is Health and Production under the Minis- and 29.95 ± 0.18 (SE) respectively. In needed to identify trypanosome species try of Agriculture introduced an odour- Shakawe, these were 21.17 ± 0.16 (SE) using available molecular markers and bait technique (OBT) in 1992 after using and 30.85 ± 0.24 (SE) in positive and isoenzyme characteristics. annual aerial sprays for 20 years, in view negative cases respectively. There was Some animals suspected of trypanoso- of its popularity among Tsetse Control a significant reduction (P < 0.05) in mosis in 16 cattle crush-pens had report- authorities throughout Africa. Resur- the haematocrit values in the trypano- edly received treatment with diminazene gence of trypanosomosis can be attrib- some-affected animals that corresponds aceturate before this survey. The crush- uted to a general upsurge of the tsetse with the observations of others1,2,9,15. The pens were Shashe, Maphane, Komkog, population and expansion of the tsetse- decrease in the haematocrit values indi- Maun West, Matsebe I, Kandalangodi, infested area from 5000–7000 km2 to cating anaemia in animals with trypano- Etsha 6, Tubu and Gumare in the Maun 11 500 km2. This was probably due to somosis is reported to be due to increased veterinary district and Seronga, Xhao, failure to monitor and re-service approxi- breakdown of erythrocytes during the Gunitsoga, Ndorotsha, Eretsha, Beetsha mately 25 000 deltamethrin-impregnated development of parasitaemia11,13. Several and Teekae in the Shakawe veterinary targets deployed around the Okavango mechanisms have been described as re- district. Berenil has been shown to have a Delta under OBT. These targets became sponsible for the destruction of erythro- limited prophylactic action against trypa- inaccessible as a result of heavy floods in cytes, which include haemolysins and nosomosis4. It is difficult to know whether the delta and adjoining areas in 1999.

0038-2809 Jl S.Afr.vet.Ass. (2001) 72(4): 232–234 233 Lack of reliable and suitable transport also tsetse is not achieved by OBT and aerial pathology of animal trypanosomosis. In restricted access to targets. Apart from spraying. Mulligan H W (ed.) The African trypano- somiasis. George Allen and Unwin/Ministry this, Ngamiland has a fairly naive cattle of Overseas Development, London: 729– population after restocking a little over 3 ACKNOWLEDGEMENTS 750 years ago from nagana-free areas as a We thank Dr M V Raborokgwe, Direc- 9. Griffin L, Allonby E W,Preston J W 1981 The result of an outbreak of contagious bovine tor, Department of Animal Health and interaction of Trypanosoma congolense and pleuropneumonia in the area. Exposure Production, Ministry of Agriculture, Haemonchus contortus infections in two Botswana, for granting permission to breeds of goats. I. Parasitology. Journal of of such animals to a fairly large popula- Comparative Pathology 91: 85–95 publish this paper, and officers at the tion of vector flies, besides stress of over- 10. Masake R A 1997 Diagnosis of African crowding and limited grazing areas on Maun and Shakawe veterinary districts trypanosomosis (Review). In OAU/STRC, account of floods and heavy rains, might offices and the Tsetse Control Division for 1997: 69–77 have exacerbated the severity of trypano- their assistance in the collection of blood 11. Murray M, Dexter T M 1988 Anaemia in samples. bovine African trypanosomiasis: a review. somosis. Acta Tropica 45: 389–432 The Government of Botswana ap- REFERENCES 12. Murray M, Morrison W I 1979 Pathogenesis and pathology of African trypanosomiasis in proved and implemented a 3-phased 1. Abebe G, Jobre Y 1996 Trypanosomiasis: domestic livestock. Food and Agriculture integrated tsetse control strategy in a threat to cattle production in Ethiopia. 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